Dnd 5e Ability Score Calculator

by
DC
David Chen Senior Mechanical Engineer & CNC Consultant
This professional Countersink Calculator helps machinists and engineers quickly determine the required diameter, depth, or angle for conical holes. Whether you are prepping for flathead screws or deburring, use this tool to ensure precision in your fabrication process.

Countersink Calculator

Leave one field blank to solve for it. Requires at least 3 values.

Outer diameter of the countersink
The pre-drilled through-hole diameter
Included angle (standard: 82°, 90°, 100°)
Depth from surface to the intersection
Result
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Please enter exactly 3 values to solve for the 4th.
Steps will appear here after calculation.

Countersink Calculator Formula

tan(A / 2) = (D – d) / (2 * h)

To solve for specific variables, we use:

  • Major Diameter (D): d + 2 * h * tan(A/2)
  • Depth (h): (D – d) / (2 * tan(A/2))
  • Hole Diameter (d): D – 2 * h * tan(A/2)

Source: Engineering Toolbox | Wikipedia – Countersink

Variables:

  • Major Diameter (D): The largest diameter of the conical opening at the surface.
  • Minor Diameter (d): The diameter of the pre-existing pilot hole or through-hole.
  • Angle (A): The total included angle of the countersink tool.
  • Depth (h): The vertical distance from the material surface to the bottom of the taper.

Related Calculators

What is a Countersink Calculator?

A countersink calculator is a geometric tool used in machining to determine the dimensions of a conical hole. This is primarily used so that the head of a flat-head bolt, screw, or rivet can sit flush with or below the surface of the material.

In precision manufacturing, knowing the exact depth to feed a tool is critical. If the depth is too shallow, the screw will protrude; if it is too deep, the material might be weakened or the screw might sink too far.

How to Calculate Countersink Dimensions (Example)

Suppose you have a 0.250″ through-hole and an 82-degree flat-head screw that has a 0.500″ head diameter. How deep should you drill?

  1. Identify variables: D = 0.500, d = 0.250, A = 82°.
  2. Find tan(A/2): tan(41°) ≈ 0.8693.
  3. Apply formula: h = (0.500 – 0.250) / (2 * 0.8693).
  4. Calculate: h = 0.250 / 1.7386 ≈ 0.1438″.

Frequently Asked Questions (FAQ)

What is the standard angle for a countersink?

Standard angles are usually 82° (common in the US for machine screws), 90° (metric standard and deburring), and 100° (aerospace/flat rivets).

Can I calculate depth if I don’t know the hole diameter?

Yes, but you usually assume the hole diameter (d) is the diameter of the screw shank. If d is zero (a pointed tip), the depth is simply half the major diameter divided by the tangent of half the angle.

Why does my screw not sit flush?

This often happens if the “Major Diameter” used in calculations is exactly the same as the screw head. Machinists often add 0.010″ to 0.015″ to the Major Diameter to ensure the screw sits slightly below the surface.

What is the difference between countersink and counterbore?

A countersink is a conical (V-shaped) hole for flat-head screws. A counterbore is a cylindrical (flat-bottomed) hole for socket head cap screws.